As urban centers increase in size, and traffic congestion becomes increasingly a problem, there is a concomitant increasing need for current and accurate traffic statistics and information. Traffic surveillance relies primarily upon traffic sensors, such as (1) inductive loop traffic sensors, which are installed under the pavement; (2) video sensors; (3) acoustic sensors; and, (4) radar sensors. Inductive loop sensors, which are installed under the pavement, are expensive to install, replace and repair, both in terms of roadwork required and in terms of the disruption to traffic. In contrast, video sensors, acoustic sensors and radar sensors are easier to install, replace and repair. They have the added advantage of multi-lane detection by a single sensor. On the other hand, their accuracy depends on centering their detection zones on traffic lanes.
Video sensors typically detect vehicles based on recognizable automobile characteristics. Acoustic sensors rely on sound waves to build up a picture of traffic conditions. Radar sensors typically transmit low-power microwave signals at the traffic, and detect vehicles based on the reflected signals. However, all of these sensors require initial detection zones or lanes to be defined in order to operate accurately.
This calibration of detection zones or lanes in sensors may be provided by a technician. However, this is expensive both in terms of paying the technician, and due to the resulting disruption of traffic. Alternatively, detection zones may be defined automatically and automatically centered on traffic lanes.